IATA vs ICAO: What Is the Difference
IATA and ICAO airport codes explained in plain language. Why Sheremetyevo is both SVO and UUEE, how three-letter and four-letter codes are structured, where passengers and specialists meet each one, and why the codes never match.
IATA vs ICAO: Why One Airport Has Two Codes
Look closely at Moscow Sheremetyevo and you will find it labelled two different ways: SVO on your boarding pass and UUEE on an air traffic control chart. Both are correct, and both point to the same airport. The reason is that aviation runs on two parallel coding systems - one built by IATA for passengers and commerce, and one built by ICAO for operations and regulation. This guide explains the difference, how each code is structured, and where you actually meet them.
Why Two Standards Exist
The two systems were created by different organizations to solve different problems, and they were never meant to be the same thing.
- IATA - the International Air Transport Association - is an airline trade body. Its three-letter codes are optimized for the commercial world: ticketing, reservations, baggage handling and departure boards. They are short, easy to say, and easy to print on a luggage tag.
- ICAO - the International Civil Aviation Organization - is a United Nations agency that sets global aviation standards. Its four-letter codes are optimized for operations and safety: air traffic control, flight plans, and aeronautical documents. They are structured geographically so that a controller can tell at a glance where in the world an airport sits.
Because the two bodies pursue different goals, their codes follow different logic and rarely line up. That is by design, not by accident.
How the Codes Are Structured
IATA Codes (3 Letters)
IATA airport codes are three letters assigned by IATA. They carry no geographic logic - the letters are usually a mnemonic drawn from the airport or city name (LAX for Los Angeles, DXB for Dubai) or a historical abbreviation (SVO for Sheremetyevo). Because there are only 17,576 possible three-letter combinations, IATA reserves them mainly for airports with scheduled commercial passenger service. If a code appears on a ticket, a boarding pass or a baggage tag, it is almost always the IATA code.
ICAO Codes (4 Letters)
ICAO airport codes are four letters assigned by ICAO, and they are organized regionally. The first letter (and often the second) identifies a part of the world, so the code itself tells an operator where the airport is:
- U - Russia and most former Soviet states (UUEE Sheremetyevo, ULLI Pulkovo)
- K - the contiguous United States (KJFK New York, KLAX Los Angeles)
- EG - the United Kingdom (EGLL Heathrow, EGKK Gatwick)
- ED - Germany (EDDF Frankfurt, EDDM Munich)
- LF - France (LFPG Charles de Gaulle, LFPO Orly)
- OM - the United Arab Emirates (OMDB Dubai)
This regional structure means the four-letter space is far larger and covers virtually every airfield, heliport and small strip in the world - not just the ones with airline service.
Side-by-Side Examples
| Airport | City | IATA | ICAO |
|---|---|---|---|
| Sheremetyevo | Moscow | SVO | UUEE |
| Pulkovo | St Petersburg | LED | ULLI |
| John F. Kennedy | New York | JFK | KJFK |
| Heathrow | London | LHR | EGLL |
| Charles de Gaulle | Paris | CDG | LFPG |
| Dubai International | Dubai | DXB | OMDB |
You can look up either code for any airport using our airport code lookup, which shows the IATA and ICAO identifiers side by side.
Key Differences at a Glance
| Aspect | IATA | ICAO |
|---|---|---|
| Length | 3 letters | 4 letters |
| Assigned by | IATA (airline trade body) | ICAO (UN agency) |
| Structure | Mnemonic, no geographic logic | Region-coded by first letters |
| Coverage | Mainly commercial airports | Nearly every airfield worldwide |
| Primary audience | Passengers, travel industry | Pilots, controllers, regulators |
| You meet it on | Tickets, tags, boards | Flight plans, charts, METAR |
Where Each Code Shows Up
What Passengers See (IATA)
As a traveller you deal almost exclusively with IATA codes. They appear on your ticket and boarding pass (SVO-JFK), on the printed tag wrapped around your checked bag, on the departure and arrival boards in the terminal, and inside booking sites and airline apps. When a website asks for your origin and destination airport, it wants the three-letter IATA code.
What Specialists Use (ICAO)
Behind the scenes, professionals rely on ICAO codes. A filed flight plan uses ICAO identifiers for departure, destination and alternates. Air traffic control, aeronautical charts and NOTAMs use them too. Weather reports such as METAR and TAF are keyed to the four-letter ICAO code - a briefing for Heathrow reads as EGLL, never LHR. Because ICAO codes cover small airfields that have no IATA code at all, they are the only reliable identifier for general aviation.
Why the Codes Do Not Match
Since IATA and ICAO codes are issued by different bodies for different purposes, there is no rule forcing them to align. SVO and UUEE describe the same runway from two unrelated systems.
There is one partial exception that causes confusion: in the contiguous United States the ICAO code is simply the letter K in front of the IATA code, so JFK becomes KJFK and LAX becomes KLAX. This is a lucky consequence of the US regional rule, not a global pattern. Everywhere else the two codes are independent - Heathrow is LHR and EGLL, Sheremetyevo is SVO and UUEE, and there is no way to derive one from the other. The only reliable method to translate between them is to look the airport up in a database.
Frequently Asked Questions
Why does one airport have two different codes?
Because two organizations code airports for two different reasons. IATA assigns short three-letter codes for commercial travel, while ICAO assigns structured four-letter codes for operations and air traffic control. Both refer to the same physical airport.
Why do the codes not match, like SVO versus UUEE?
They come from independent systems with no requirement to agree. IATA codes are mnemonic; ICAO codes are geographic. Except for the K-prefix coincidence in the United States, you cannot calculate one from the other.
Which code is on my ticket?
The IATA three-letter code. Tickets, boarding passes, baggage tags and departure boards all use IATA. You will only encounter ICAO codes if you read flight plans, aviation charts or aviation weather reports.
Does every airport have both codes?
No. Almost every airport with scheduled commercial flights has both, but thousands of small airfields, private strips and heliports have only an ICAO code and no IATA code, because IATA codes are reserved mainly for commercial service.
Can I convert an IATA code to an ICAO code automatically?
Not with a formula. Outside the US K-prefix case there is no reliable conversion rule, so you need a reference source. Our airport code database lets you enter either code and see the matching one instantly.
In short: IATA is the language of the passenger and ICAO is the language of the cockpit and control tower. Knowing which is which turns a confusing pair of labels - SVO and UUEE - into two clear views of the very same airport.